The present invention relates to a flying type thin film magnetic head of a disc drive. In particular, the present invention relates to a top surface insulating layer of a thin film magnetic head slider.
Conventional thin film magnetic heads typically have a write/read transducer provided on a trailing end surface of the magnetic head slider. Each write/read transducer includes several bond pads located on a trailing end surface of the slider. The bond pads are provided for electrically connecting the read/write transducer with connecting wires extending from the control circuitry of the disc drive. However, providing the bond pads on the trailing end surface of the slider becomes a limiting factor on miniaturization of the magnetic head slider because connecting wires from the control circuitry need to be secured to the bond pads on the trailing end surface of the slider. This is a difficult, time consuming, and expensive process because of the small surface area available on the trailing end surface of the slider for making the electrical connections between the connecting wires and the bond pads. Moreover, in addition to this difficult electrical connection, a separate mechanical connection is required to connect the slider with the support arm carrying the slider.
FIG. 1 of the Ainslie et al. U.S. Pat. No. 4,789,914 illustrates a typical prior art configuration. However, the Ainslie et al. patent also discloses a thin film magnetic head head/slider in which the top surface of the slider includes a pair of contact pads 39 (see FIG. 3 of Ainslie patent) adapted for mechanically connecting the support arm with the slider and for electrically connecting the control circuitry of the disc drive with the connecting links from the read/write transducer. The read/write transducer is adjacent the trailing end surface of the slider and adjacent the air bearing surface of the slider. The solder contact pads 39 are connected to the read/write transducer and replace bond pads which were previously provided on the trailing end surface of the head/slider for electrical connection with connecting wires from the control circuitry.
Although placing solder contact pads 39 on a top surface of the slider provides a simpler mechanical and electrical connection, this design presents problems associated with signal quality resulting from ineffective electrical isolation between conductive components. In particular, the substrate of a slider is a conductive material and comprises a majority of the body of a slider. The contact pads 39 are also conductive and therefore must be electrically isolated from the conductive substrate of the slider. Accordingly, as shown in FIG. 10 of the Ainslie patent, an insulating layer 17 was introduced on top of substrate 1 and over a substantial length of the slider except for the trailing end portion of the slider adjacent the connecting posts 11 (connected to the read/write transducer). The insulating layer 17 has a terminal edge adjacent and positioned over the posts 11. This edge of the insulating layer in most prior art sliders typically extends across a full width of the slider.
Despite the introduction of the insulating layer 17, poor electrical isolation can occur between the contact pads and the conductive substrate 1 in a slider assembly like that of the Ainsle patent. In addition, poor electrical isolation can occur between separate contact pads (extending on the top surface of the slider over the insulating layer). These problems of electrical isolation are primarily caused by the configuration of the insulating layer formed on the top surface of the slider.
A prior art slider is provided in FIGS. 1 and 2 of this application to illustrate the problems caused by the current prior art configuration of the top surface insulating layer of the Ainslie-type slider. In particular, a prior art slider 10 shown in FIGS. 1 and 2 includes a conductive substrate 12 and a trailing end insulator 14 made of an alumina insulating material. An insulator 16 (analogous to layer 17 in the Ainslie patent) is provided on a top surface 15 of the substrate 12 and over the trailing end insulator 14 to form a top surface 19 of the slider 10. The insulator 16 includes a terminal edge 17 extending across the width of the slider and a side edge 18 extending along the length of the slider. A first bond pad 20 (analogous to the combination of layer 21 and 25 forming part of contact pads 39 as seen in FIG. 15 of the Ainslie patent) extends across a surface of the insulator 16 and across a top surface of the trailing end insulator 14. The first bond pad 20 is electrically connected to a first connecting link 22a (FIG. 2) (analogous to posts 11 in FIG. 15 of the Ainslie patent) extending up through the trailing end insulator 14, with the first link 22a having an end 22b exposed on the top surface of the trailing end insulator 14. A second bond pad 24 extends along a surface of the insulator 16 and on a top surface of the trailing end insulator 14. The second bond pad 24 is electrically connected to a second connecting link 26a which extends up through, and has an end 26b exposed on the top surface of, trailing end insulator 14.
The insulator 16 electrically isolates the conductive first bond pad 20 and the conductive second bond pad from the conductive substrate 12.
As shown in FIG. 2, the slider 10 includes a read/write inductive-type transducer 32 disposed below an end surface 31 of the slider 10 within trailing end insulator 14 adjacent an air bearing surface 33 of the slider. The first link 22a and second link 26a are electrically connected to the transducer 32.
Optimum operation of the read/write transducer 32 requires a high degree of electrical isolation between: conductive first bond pad 20 and the conductive substrate 12; conductive second bond pad 24 and the conductive substrate 12; and conductive first bond pad 20 and conductive second bond pad 24. However, this desired electrical isolation cannot always be achieved because a conductive metallic seed layer residue 28 sometimes remains after fabrication of first bond pad 20 and second bond pad 24, and can partially cover an edge surface 30 of the terminal edge 17 and the side edge 18 of the insulator 16. This conductive seed layer residue can reduce the impedance between respective bond pads 20 and 24 hampering the desired electrical isolation therebetween.
The conductive metallic seed layer (not shown) is used as an intermediate step to facilitate electroplating the bond pads 20 and 24. In the intermediate step, the seed layer is deposited over the entire top surface of the slider including the insulator 16, first link end 22b and second link end 26b, and the top surface of the trailing end insulator 14. After fabrication of the bond pads 20, 24, 34 and 36 (by electroplating conductive bonding material on the seed layer), any exposed seed layer is removed to yield the configuration shown in FIGS. 1 and 2. However, the current processes such as wet etching, sputter etching, and ion milling are not capable of reliably removing all of the exposed seed layer, and residual traces 28 of the seed layer thus remains on the edges 18 and 30 of the insulator 16. The seed layer residue 28 degrades the desired electrical isolation between the electrically active components, i.e., the bond pads and the substrate. In particular, the seed layer residue 28 can provide an unwanted electrical connection between bond pads 20 and 24, between first bond pad 20 and substrate 12, or between second bond pad 24 and substrate 12.
However, the seed layer residue alone does not cause the electrical isolation difficulties. Rather, the terminal edge 17 of the insulator layer 16 primarily creates the electrical isolation problems because the edge surface 30 of the terminal edge 17 is common to several separate conductive components. As seen in FIG. 1, the edge surface 30 is common to the conductive substrate 12, the conductive bond pads 20 and 24 as well as any other conductive bond pads such as bond pads 34 and 36. This commonality of edge surface 30 with all of the respective conductive components permits the conductive seed layer residue 28 on the edge surface 30 of edges 17 and 18 to degrade the desired high impedance between the respective conductive components, namely, the substrate 12 and bond pads 20, 24, 34 and 36.
Placing bond pads of a read/write transducer on a top surface of a slider provides considerable advantages. However, it is desirable to modify the currently known assembly of the top surface of the head/slider, particularly the top surface insulating pattern, to overcome the problems of ineffective electrical isolation between conductive bond pads such as bond pads 20 and 24, and between each of the respective conductive bond pads and the conductive substrate 12. These isolation problems are caused by the edge surface 30 of the insulator 16 being common to each respective electrically active components (e.g., substrate 12, bond pads 20 and 24) such that the conductive seed layer residue 28 on the edge surface 30 of edges 17 and 18 of insulator 16 degrades the desired high impedance between the respective electrically active components.